Magnesium (Mg) and its alloys have gained wide popularity in the biomedical field as promising candidates for degradable implant applications. Among Mg alloys, AZ (aluminum and zinc) series alloys are the most widely investigated for implant applications and reported in the literature. In all AZ series Mg alloys, aluminium content is the influencing factor that imparts different properties to the Mg alloys. In the present study, pure Mg, AZ31 and AZ91 Mg alloys were selected and the effect of aluminium content on the biocorrosion has been investigated in Ringer’s solution. It was a clear observation that the increased aluminum content has a severe effect on the degradation behavior of magnesium. From the weight loss measurements, AZ31 has shown lower corrosion rate compared with pure Mg and AZ91. The surface morphologies also showed the formation of more pits on pure Mg and AZ91 Mg alloy compared with AZ31 Mg alloy. By correlating the degradation behavior with the microstructure, galvanic corrosion was found to be the main reason behind the accelerated corrosion rate in AZ91 Mg alloy compared with AZ31 alloy. The phases on the corroded sample surfaces were examined by X-ray diffraction (XRD) method and scanning electron microscopy (SEM) and found that the corrosion products which were deposited on the surfaces provided protection against the chloride ions which was indicated by the decreased corrosion rates as immersion time was increased
